Table of Contents
- What a Big Bore Kit Installation Actually Costs
- Parts Cost: What the Kit Itself Sets You Back
- Big Bore Kit Labour Cost: Shop Rates and Hours
- Big Bore Kit Installation Time: DIY vs Professional
- Big Bore Kit Machine Work: What Gets Bored and Why
- Big Bore Kit ECU Tuning: The Cost You Can't Skip
- Hidden Costs, Warranty and Long-Term Ownership
- Frequently Asked Questions
Last Updated: October 18, 2026
What a Big Bore Kit Installation Actually Costs
A motorcycle big bore kit installation cost typically lands between the price of the kit itself and roughly double that figure once labour, tuning and machine work are added. At SSS Motorcycles, we see riders budget for the hardware and forget the rest. The kit is only half the invoice.
Here is the honest breakdown. A big bore conversion increases engine displacement by fitting a larger cylinder bore and piston, which means the top end comes apart, the fueling gets remapped, and someone has to do the work properly. Miss any of those steps and you get a bike that runs worse than stock.
Below, we'll show you exactly what each stage adds to the total, so you can quote the job with your eyes open.
Parts Cost: What the Kit Itself Sets You Back
Parts cost is the one number most riders already know, and it is the easiest to control. We sell complete cylinder kits rather than bare pistons, because a big bore piston without the matching cylinder, gaskets and ECU work is a paperweight. Every kit below includes the hardware and the mapping needed to make it run.
| Kit | Displacement | Price | Best For |
|---|---|---|---|
| SSS Stage 3.0 | 301cc | $1,350 | Budget-conscious riders wanting proven gains |
| SSS Stage 3.25 | 325cc | $1,790 | Riders chasing maximum usable power |
| SSS Upgrade Kit | Stock capacity | $1,150 | Riders not ready for engine work |
| Stage 3.5 Camshaft Set | Add-on | $515 | Stage 3.0 owners wanting top-end pull |
Stage 3.0 301cc Kit: $1,350
The SSS Stage 3.0 301cc Big Bore Kit is our entry point into engine displacement. It pairs a 78mm piston with a genuine Honda cylinder bored in house, a Stage 3 ECU and a top-end gasket kit. Outright purchase, no exchange, and delivery is included. Lead time runs about three weeks.
Stage 3.25 325cc Kit: $1,790
Step up to the SSS Stage 3.25 325cc Big Bore Kit and you get an 81mm piston, a resleeved cylinder, ECU reflash, Velocity intake stack, second snorkel and airbox vent. Choose 32HP, or 34HP with adjustable camshafts. This one ships from stock.
Big Bore Kit Labour Cost: Shop Rates and Hours
Big bore kit labour cost is where budgets quietly blow out, and it is the number most quotes hide. A top-end rebuild is not a quick bolt-on. The tank, bodywork and airbox come off, the head and cylinder are removed, the piston is swapped, and everything goes back together to Honda torque specifications.
Rather than quote one figure that applies to no bike in particular, it helps to understand what drives the hours. Three things dominate:
- Engine access. On a naked or dual-sport single, the top end is reachable with the tank and seat off. On a faired multi-cylinder machine, bodywork, radiator and sometimes the engine itself have to come out, and that is where labour multiplies.
- Cylinder configuration. A single-cylinder top end is one piston, one bore, one head. A parallel-twin or V-twin doubles the piston and ring work and adds more head bolts to torque in sequence.
- Whether the cylinder is exchanged or sent away. A pre-machined or resleeved cylinder that arrives ready to fit removes a wait and a handling step. Sending your own cylinder in adds turnaround time and a second round of fitment checks.
As a planning rule, most practitioners find a single-cylinder top-end conversion books in the region of a full working day of mechanical labour, while faired or multi-cylinder machines can run to two days or more once bodywork and engine removal are counted. Treat those as planning ranges, not quotes, the only reliable number is the one your workshop puts in writing after seeing the bike.
Shop rates vary by workshop and region, so ask for an hourly figure in writing before you commit, and ask what the job is capped at. A shop that quotes a flat fee is usually safer than one billing open-ended hours, because the flat fee transfers the risk of a seized fastener or a stubborn gasket to the workshop rather than to you.
How to read a labour quote
When you compare quotes, put them side by side on the same four lines: mechanical hours, machine work, ECU remap, and consumables. A quote that looks cheaper on the headline often excludes the remap or the gaskets, and those reappear on the final invoice. Ask each workshop to state:
- The hourly rate and the estimated hours, separately.
- Whether the cylinder is supplied pre-machined or bored locally.
- Whether the ECU remap and a post-build test ride are included.
- What happens if additional work is found once the top end is open, and how that is priced.
That checklist turns a vague "several hours" into a number you can actually budget against.
Big Bore Kit Installation Time: DIY vs Professional
Big bore kit installation time depends entirely on who holds the spanner. An experienced mechanic works efficiently because the disassembly sequence is familiar. A first-timer should set aside a full day or more, and that assumes no snapped bolts or seized fasteners.
Professional installation buys you two things: speed and a paper trail. Our warranty on the Stage 3.25 kit applies when installation is performed by SSS Motorcycles.
DIY saves the labour charge but costs you time, tools and risk. If you have never set piston ring end gaps or torqued a cylinder head in sequence, this is not the job to learn on.
CRF300 SSS STAGE 3.25 BIG BORE KIT 325CC DEVELOPED FOR AUSTRALIAN FUELS ⛽️ →
Big Bore Kit Machine Work: What Gets Bored and Why
Big bore kit machine work is the step riders underestimate most. A larger piston needs a larger cylinder bore, and that bore has to be machined to the exact piston clearance the manufacturer specifies. Get it wrong and you get piston slap, oil consumption or a seized top end.
This is why we bore cylinders in house and supply resleeved units. The fitment is checked before the kit leaves us, not discovered halfway through your rebuild. If you send your own cylinder in, expect turnaround time on top of the machining itself.
Big Bore Kit ECU Tuning: The Cost You Can't Skip
Big bore kit ECU tuning is not optional, and treating it as optional is the most common mistake we see. More displacement moves more air, and the factory fuel map was never written for it. The engine needs revised fueling and ignition timing to make power safely.
Every SSS big bore kit ships with matching ECU mapping because the two are designed as one system. The SSS Stage 2.2 Velocity Upgrade Kit shows the same principle at stock capacity: airflow changes require mapping changes, and running the Velocity intake stack on standard mapping is something we specifically advise against.
Hidden Costs, Warranty and Long-Term Ownership
Hidden costs are the difference between a quoted price and a real one, and almost no guide itemises them. Here is the full list to budget against, beyond the kit and the labour:
- Gaskets and seals. A top-end gasket kit is usually bundled with a complete kit, but if you are assembling from parts, head, base and cam-cover gaskets plus valve-stem seals add up.
- Machine work. Boring or resleeving a cylinder is a separate line from labour. A kit that arrives pre-machined removes this cost; sending your own cylinder in adds it, plus turnaround time.
- ECU remap or reflash. Treat this as mandatory, not optional. If a quote does not include it, add it before you compare totals.
- Fluids and filters. Fresh engine oil and filter, and coolant if the cooling system is drained for access.
- Break-in service. A short-interval oil and filter change after the first few hundred kilometres, plus a check of torque and valve clearance.
- Clutch and driveline. More torque can surface a worn clutch earlier than expected. Budget for plates if the bike has covered significant distance.
- Fasteners and consumables. Head bolts, circlips and any single-use fasteners the workshop manual says to replace.
- Freight. If you are sending a cylinder away or having a kit delivered, factor shipping both ways.
Add those to the kit price and the labour estimate and you have a realistic out-the-door figure rather than a hardware price that doubles on collection day.
Warranty and your statutory rights
Warranty deserves a close read. Our six-month cover applies when SSS Motorcycles performs the installation, and it sits alongside your statutory rights under the Australian Consumer Law, those rights are not displaced by any manufacturer warranty. Liability under our cover is limited to repair or replacement of the product, with no labour costs included.
Long-term ownership costs
Long term, reliability comes down to break-in discipline and maintenance. Follow the Honda workshop manual for torque figures, use the lubrication method we specify during assembly, and keep up with oil changes. A common pattern is that the first service after a big bore conversion matters more than any that follow, because it is the point where ring seating and any early fitment issues show up.
Budget for slightly more frequent oil changes than a stock engine, and keep an eye on valve clearance during the first few services. Do that and a well-installed big bore conversion is a dependable performance upgrade rather than a grenade with a pin in it. Skip the break-in service and the savings you made on labour reappear as a top-end rebuild.
Frequently Asked Questions
How much does a motorcycle big bore kit cost to install?
The kit is only part of the bill. A CRF300 big bore kit runs from $1,350 for the Stage 3.0 301cc to $1,790 for the Stage 3.25 325cc, and that price already includes the cylinder, piston, gaskets and ECU mapping. Labour is the variable: a licensed mechanic typically needs several hours for a top-end rebuild, and shop rates vary by workshop. Ask for a fixed quote that lists parts, labour hours and any machine work separately so there are no surprises.
How many labour hours does a big bore kit installation take?
It depends on the kit and the bike. SSS quotes 4 to 6 hours for a first-timer fitting the Stage 2.2 Velocity kit, and 1 to 2 hours for an experienced mechanic, largely because the airbox is awkward to remove. A full big bore conversion with cylinder and piston replacement adds engine disassembly and top-end rebuild time on top. Budget for a full day if you are doing it yourself for the first time.
Does a big bore kit need ECU tuning?
Yes. A larger cylinder and piston change how much air the engine moves, so the standard fuel map runs lean. Every SSS big bore kit includes an ECU reflash matched to the kit, and the Stage 3.25 ships with Stage 3.25 mapping. Running a big bore on stock mapping risks poor running and engine damage. SSS also warns that the Velocity intake stack should never be used with standard mapping because above 8500rpm the engine needs substantially more fuel.
Is it cheaper to install a big bore kit yourself?
On paper yes, because you skip the labour charge. In practice the kit is intended for licensed, experienced motorcycle mechanics, and SSS accepts no liability for damage caused by improper installation, lubrication or mechanical inexperience. Getting piston ring sealing and torque specs wrong can cost more than the labour you saved. If you are not confident with a top-end rebuild, pay a workshop and keep the warranty intact.
What machine work might a big bore kit require?
A big bore conversion needs the cylinder bored or resleeved to match the larger piston. SSS does this in house: the Stage 3.0 kit uses a genuine Honda cylinder bored to 78mm, and the Stage 3.25 kit uses a resleeved cylinder with an 81mm piston. If you send your original cylinder in, it is machined to suit. Always confirm whether machine work is included in the kit price or charged separately before you commit.